Dinosaurs were originally envisioned as giant lizards. Then, during the late 19th century, they started to look more active — more similar to mammals and birds than to lizards. The prevailing logic changed again during the 20th century, generally depicting dinosaurs as sluggish and dim-witted, only to be reversed back to the late 19th-century view of active, dynamic animals. So where does the evidence stand now?
Part of the problem is the phrase “warm-blooded.” It doesn’t really have much to do with temperature alone. The phrases "warm-blooded" and "cold-blooded" are often used to distinguish animals that can regulate their own body temperatures internally (endothermic), and those whose body temperatures change with their environment (ectothermic). In this way, an ectothermic animal like a turtle can be “warm-blooded” while out in the sun, but “cold-blooded” in the shade.
Unpacking the physiology of dinosaurs would be an article in and of itself; but, ...
